1. Field of the Invention
The invention relates to a method for error-protective encoding of data. The method includes:
encoding the data by an error protecting code to encoded data PA1 storing the encoded data in a medium as stored data PA1 reading the stored data from the medium and comparing with the encoded data. PA1 upon detecting a particular discrepancy between stored data and encoded data generating a discrepancy identifier PA1 storing the discrepancy identifier in association with the stored data as stored identifier, thereby raising error protection offered by said error protecting code. PA1 an error protecting encoder for encoding the data to encoded data PA1 memory apparatus for storing the data PA1 memory access apparatus for writing the encoded data in the memory as stored data and for reading the stored data from the medium PA1 comparing apparatus connected to said access apparatus for comparing the encoded data with the stored data. The device further includes PA1 secondary encoding apparatus fed by the comparing apparatus for generating a discrepancy identifier, under control of detection of a particular discrepancy between stored data and encoded data, for presentation to said memory access means. The memory access apparatus then stores the discrepancy identifier with the stored data a yielding stored identifier as additional error protection for said stored data. A device of this kind can be realized in a straightforward manner, starting from the idea of the present invention, and using elementary hardware.
2. Related Art
Various earlier encoding organizations have been disclosed in U.S. Pat. No. 4,567,518 (PHN 10221), EP-A1 437 865, corresponding U.S. patent application Ser. No. 08/419,483 and U.S. Pat. No. 5,467,360 (PHN 13213), EP A1 603 932, corresponding U.S. patent application Ser. No. 08/167,266 (PHN 14311), EP Patent Application 698,269, corresponding U.S. patent application Ser. No. 08/535,155 (PHN 15107), all assigned to the present assignee. Many recording schemes provide for a check read-out directly after writing. Upon detecting a discrepancy, the storing may be undertaken a second time, either at the same storage location, or at another storage location. The policy with respect to the latter choice is determined by various factors. A first one is the character of the interference, that may be hard or soft. A second one is the organization of the storage, that may be random accessible, quasi-random accessible, or serial. Still further considerations may play a part. The present invention has with respect to the above methodology taken into account the general requirement for saving space as well as time. In consequence, any required additional storage space should be limited. On the other hand, a full second storage run would often cost too much time. A different consideration is that many applications allow increasing the complexity of an encoder if thereby the complexity of the decoder can be lowered. In fact, encoders are often implemented in a professional environment, whereas decoders are rather more frequently used at consumer premises.